Field of the Invention
The present invention relates generally to security systems for doors, and more particularly to an improved security system for use with an electrically operated door locking mechanism, which security system is operative to provide a preset delay following an effort to exit through the controlled door before actuating the door locking mechanism to unlock the door and allow egress.
Security doors have evolved over the years from simple doors with heavy duty locks to sophisticated egress and access control devices. In bygone times, heavy duty chains and locks were the norm on security doors which were not generally used, or which were used to prevent theft or vandalism. However, fire codes have made such relatively simple door locking systems obsolete, at least in most developed countries. Emergency exit doors are required by law to be provided in all commercial buildings, and such doors must be operative in the event of a fire, earthquake, or other emergency.
These exit doors are typically provided with heavy horizontal push bars, which unlock the door upon actuation and which may provide an alarm of some sort. The early alarms on such doors were either mechanical in nature, such as wind-up alarms contained on the push bar mechanism, or completely separate electrical circuits actuated by a switch opened as the door was opened. Accordingly, egress from such doors was immediate, and, although egress was accompanied by an alarm, typically the person leaving through the door was long gone by the time security personnel arrived.
Many stores suffer great losses through emergency doors, with thieves escaping cleanly through the emergency doors with valuable merchandise. In addition, industrial companies also suffer pilferage of valuable equipment and merchandise through such emergency exit doors. While one solution is to have a greater number of security personnel patrolling the emergency exit doors, to do so is also an expensive solution.
As might be expected, the art reflects a number of devices which attempt to solve this problem. A series of such devices is found in U.S. Pat. No. 4,257,631, in U.S. Pat. No. 4,328,985, in U.S. Pat. No. 4,354,699, in U.S. Pat. No. 4,652,028, and in U.S. Pat. No. 4,720,128, all to Logan, Jr. or Logan, Jr. et al. The Logan, Jr. patents begin with the Logan, Jr. '631 patent, which describes a system activated by a push bar which, upon depression, moves a switch carried by the door to sound an alarm and start a timer delay. After the delay, the door is unlocked.
The Logan '985 patent teaches a hydraulic system for accomplishing the delay prior to unlocking the door, and the Logan '699 patent describes a retrofit locking device of the same type, but usable with any door latching system. The Logan et al. '028 patent and the Logan, Jr. et al. '128 patent both teach an electromagnet mounted on a door jamb, an armature on the door held by the electromagnet to retain the door in the closed position, and a switch used to indicate when the door is being opened or tampered with. The Logan, Jr. et al. '128 patent adds a set of contacts to confirm that the armature properly contacts the electromagnet.
U.S. Pat. No. 4,439,808, to Gillham, describes another system which also uses an armature on a door and an electromagnet on the door jamb. The armature has shoulders to retain the door in the closed position even if someone exerts enough pressure on the door to otherwise slide the armature off of the electromagnet. U.S. Pat. No. 4,439,808, to Gillham, is hereby incorporated herein by reference.
Two other patents are relevant, particularly since they are both assigned to the assignee of the present invention. Specifically, these patents are U.S. Pat. No. 4,609,910 and U.S. Pat. No. 5,000,497, both to Geringer et al. The Geringer et al. '910 patent teaches a system with an armature on a door, an electromagnet on a door jamb, and a switch used to tell when an attempt is made to open the door. The Geringer et al. '497 patent teaches a novel door-mounted armature and door jamb-mounted electromagnet. U.S. Pat. No. 4,609,910 and U.S. Pat. No. 5,000,497 are both hereby incorporated herein by reference.
While these references represent a substantial improvement in the state of the art to date, there are still several disadvantages and problems inherent in the art. For example, in an emergency, someone trying to get out will find that the door does not immediately open, and may panic and leave the door prior to it opening after a delay. In addition, the present devices may not fully comply with safety regulations, and thus may no longer be commercially competitive.
It is accordingly the primary objective of the present invention that it provide a security system which, when actuated by someone trying to open the door, will provide information about the delay imposed before the door will be opened. Such information must serve to inform the individual that the door will be opened following a short delay. It is also desirable that the exact period of the delay be made known to the individual.
It is also an objective of the present invention that the security system taught therein operate to unlock the door after a preset period of time, with that preset period being adjustable in duration. In addition, it is an objective that the system operate to ensure that the lock will operate in a fail-safe mode in the event of a fire or another bona fide emergency, operating all doors in the affected area. Also, it is an objective that the system allow immediate egress or access to a security officer. It is an additional objective that the system provide information on its operation to a single remote location.
The security system apparatus of the present invention must also be of a construction which is both durable and long lasting, and it should also require little or no maintenance to be provided by the user. In order to enhance the market appeal of the security system of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the present invention be achieved without incurring any substantial relative disadvantage.